A coke oven normally has a battery of coking chambers of rectangular horizontal outline that are separated from one another by heated walls defining their longer sides and are open at their two narrower horizontal ends. These ends are provided with the doorjambs against which respective coke-oven doors can snugly fit during the coking operation to hold the charge in the respective chamber and to prevent the escape of gases and heat from the chamber. These doors, as described on pages 120 ff of The Making, Shaping and Treating of Steel by H. McGannon (Herbick & Hood:1971), each have a rigid panel with a periphery complementary to the respective doorjamb. A seal is provided at this periphery for forming a gastight connection between the periphery and the doorjamb, and holding structure is provided to press the door tightly over the respective doorjamb. Extending inwardly from the inner face of this panel is a vertically elongated and horizontally projecting plug of refractory insulating material that extends into the respective coking chamber. The insulating plug prevents the door from being heated excessively while similarly preventing the ends of the charge inside the chamber from being inadequately coked because of excessive cooling. Gases generated during the coking operation normally are drawn off from the space formed between the upper level of the charge and the roof of the chamber.
The plugs normally project some 400 mm from the doors into the chambers and serve to protect the iron door parts. These plugs are conventionally formed of a plurality of interfitting refractory bricks which are very heavy and relatively expensive to mount in place and maintain. Normally the chambers also have a refractory linig that projects outward roughly to the level of the refractory lining of the door, leaving a gap. As this gap fills with particulate material during use it must be meticulously cleaned after each coking operation. The inevitable thermal leakage at this gap normally also prevents complete coking of the ends of the charge, while permitting some gas leakage around the door.